The present invention relates to a rear axle for forklifts, and more particularly, to a rear axle to which bosses for supporting kingpins are welded.
Generally, in forklifts, a rear axle for supporting rear wheels is pivotally attached to a vehicle frame for the stability of the vehicle while running. As shown in FIG. 8, a rear axle 31 includes a rear axle body 34 and pairs of bosses 35a, 35b. The rear axle body 34 includes a first vertically extending plate 32 and second plates 33a, 33b, which are parallel to one another and are located on the upper and lower edges of the first plate 32, respectfully. The pairs of bosses 35a, 35b support kingpins 39a, 39b and are welded to the ends of the rear axle body 34. A center pin 36 is received in the center of the rear axle body 34. The rear axle 31 is pivotally supported through the center pin to the rear of the vehicle frame (not shown).
As shown in FIGS. 8 and 9, the bosses 35a, 35b are generally columnar and have proximal surfaces. The bosses 35a, 35b are fixed to the rear axle body 34 by engaging the proximal surfaces with the ends of the first and second plates 32, 33a, 33b and by welding the contact lines between the bosses 35a, 35b and the plates 32, 33a, 33b.
If the rear axle can constantly pivot, the stability of vehicle may degrade when the vehicle turns carrying a heavy load or when running on bumpy surfaces carrying a load at a high position.
Japanese Unexamined Patent Publication No. 58-167217, 9-309308, and 9-309309 describe a technology for locking a rear axle by a lock mechanism when a centrifugal force applied to the vehicle exceeds a predetermined value or when the position of the load exceeds a predetermined limit.
The rear axle is locked by locking a damper that is arranged between the vehicle frame and the rear axle. That is, closing a passage for supplying and draining hydraulic oil to the damper locks the damper. Also, opening the passage unlocks the damper, thus permitting the rear axle to pivot.
Reaction forces from a set of rear wheels are mostly applied to the upper bosses 35a. The reaction forces from the rear wheels increase when the rear axle 31 is locked. However, in the prior art rear axle 31, the bosses 35a, 35b have the same shape and the length of the weld beads 37 are also the same. As shown in FIG. 9 (only the boss 35a is shown), each boss 35a, 35b and the plates 32, 33a, 33b make contact over a vertical planar area, and corners formed by the contact are welded. Accordingly, only the weld beads receive the strong forces applied to the upper bosses 35a. However, the weld beads in the prior art may not provide sufficient strength.